In The Empire Strikes Back, when Vader reveals he’s Luke’s father, he puts the emphasis on the wrong word.

“He told me you killed [my father].”
“No, I am your father.” he corrects him.

But Luke already said ‘you’ in his original sentence. So when correcting him Vader should put emphasis on the word ‘am’, which is different from the word ‘killed’ in Luke’s sentence.

“No, I am your father.”